1. Field of The Invention
The present invention relates to an internal lubricating system of a swash plate type refrigerant compressor, and more particularly, to a swash plate type compressor having an internal refrigerant and lubricant separating system capable of providing a separation between an internal lubricating system from an internal refrigerant circuit in such a manner that an oil suspended refrigerant gas flowing out of a swash plate chamber is returned to the refrigerant circulating circuit after the lubricating oil component is separated and removed therefrom.
2. Description of the Related Art
A typical conventional swash plate type compressor is shown in FIG. 13, and has a front cylinder block 1 and a rear cylinder block 2 combined to form an axially extended cylinder block assembly having a horizontal axis thereof. The compressor also has a front valve plate 3 attached to the open end of the front cylinder block 1, a rear valve plate 4 attached to the open end of the rear cylinder block 2, a front housing 5 covering the front end of the cylinder block assembly, and a rear housing 6 covering the rear end of the cylinder block assembly. A swash plate chamber 7 is formed in the cylinder blocks 1 and 2 of the cylinder block assembly, and an oil sump 8 is provided in a bottom part of the cylinder block assembly, and located under the swash plate chamber 7. An axial drive shaft 9 connectable to a drive source ( not shown ) is rotatably supported by the cylinder blocks assembly via front and rear radial bearings 22 and the rotating axis of the drive shaft 9 is arranged in registration with the horizontal axis of the cylinder block assembly. A swash plate 10 is fixedly mounted on the drive shaft 9 in the swash plate chamber 7, to be rotated with the drive shaft 9. A plurality of cylinder bores 12 are formed in the cylinder blocks 1 and 2, and arranged around the rotating axis of the drive shaft 9, and a double-headed piston 13 is fitted in each cylinder bore 12 for sliding reciprocation. Each double-headed piston 13 is engaged with the swash plate 10 by ball and shoe elements 14. When the swash plate 10 is rotated about the horizontal rotating axis of the drive shaft 9 to thereby implement a wobbling motion, the pistons 13 are reciprocated in the respective cylinder bores 12 for a suction and compression of a refrigerant gas, and a discharge of the compressed refrigerant gas. The refrigerant compressor of FIG. 13 employs a forced lubrication system, for example, a forced lubrication system disclosed in Japanese Unexamined (Kokai) Utility Model Publication No. 59-107074, including an oil pump 15 provided in the rear housing 6 and driven by the drive shaft 9 to lubricate front and rear thrust bearings 11 provided between the cylinder blocks 1 and 2 and a boss of the swash plate 10, and the ball and shoe elements 14. The forced lubrication system lifts lubricating oil "A" from the oil sump 8 into a pump chamber 19, by the oil pump 15, to feed the oil "A" through a lubricating hole 20 and radial branch passageways of the drive shaft 9 to the front and rear thrust bearings 11.
Another conventional lubricating system circulates a mist of lubricating oil A through a refrigerant circulating circuit which runs through front and rear suction chambers 21 of the front and rear housings 5 and 6, the cylinder bores 12 of the cylinder block assembly. and front and rear discharge chambers 23 of the front and rear housings 5 and 6, and through the swash plate chamber 7 to lubricate the thrust bearings 11 and the ball and shoe elements 14.
In the above-mentioned conventional swash plate type refrigerant compressor, although a pressure prevailing in the swash plate chamber 7 is preferably equal to that in the refrigerant suction side, the pressure in the swash plate chamber 7 increases beyond the pressure in the suction side during the operation of the compressor, due to a blowby gas leaking from the cylinder bores 12 into the swash plate chamber 7 when compressing the refrigerant gas by the pistons 13. The swash plate chamber 7 is fluidly communicated with the suction chambers 21 by a gap in radial bearings 22, but the gap is insufficient to equalize the pressures levels of the swash plate chamber 7 and the suction chambers 21. Accordingly, a pressure equalizing hole, not shown, is usually formed between the swash plate chamber 7 and the suction side of the refrigerant circulating circuit, i.e., the suction chambers 21 and the suction passageway.
Nevertheless, in the forced lubricating system, a pressure difference between the swash plate chamber 7 and the suction side increases when the drive shaft 9 is running at a high rotating speed, for example, at 5000 rpm, and a thick mist of lubricating oil "A" flows, together with the refrigerant gas, from the swash plate chamber 7 into the refrigerant circulating circuit through short passageways connecting the swash plate chamber 7 and the refrigerant suction side. Therefore, the quantity of the lubricating oil "A" flowing out from the swash plate chamber 7 is more than that of the lubricating oil "A" flowing into the swash plate chamber 7, and accordingly, the quantity of the lubricating oil "A" reserved in the swash plate chamber 7 gradually decreases to an insufficient quantity, entailing an insufficient lubrication of the elements to be lubricated, causing the seizure of the ball and shoe elements 14, and causing a rapid abrasion of the elements. Moreover, the lubricating oil "A" discharged together with the refrigerant gas into the outer refrigerating circuit accumulates in an evaporator of the refrigerating circuit to reduce the cooling efficiency of the refrigerating circuit.
On the other hand, the lubricating system which lubricates the refrigerant circulating circuit and the swash plate chamber 7 by the mist of lubricating oil "A" separates the lubricating oil "A" from the refrigerant gas discharged into the discharge chambers 23 by an appropriate filter device, and returns the separated lubricating oil "A" to the refrigerant suction side of the compressor to prevent the lubricating oil "A" from flowing into the outer cooling circuit. Nevertheless, the filter device is unable to completely separate the lubricating oil from the refrigerant gas, and therefore, lubricating oil accumulates in the evaporator and the like of the outer refrigerating circuit to thereby reduce the cooling efficiency of the refrigerating circuit.